Transaction processing based on device location

ABSTRACT

A near field communication (NFC) system includes an NFC reader that communicates with a remote NFC device through load modulation. The NFC reader transmits a wireless carrier signal from an antenna and has a plurality of passive receive antennas to receive the modulated signal. The NFC reader also has circuitry to provide a plurality of data streams that define data recovered from the modulated wireless carrier signal received from the plurality of receivers. The circuitry then selects, based on a location of the NFC device relative to the NFC reader, one of the plurality of data streams for use in processing a transaction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/218,216, entitled “SYSTEMS AND METHODS FOR SENSING LOCATIONS OF NEARFIELD COMMUNICATION DEVICES,” filed on Dec. 12, 2018, and granted asU.S. Pat. No. 11,182,770, which is incorporated herein by reference.

BACKGROUND

Near field communication (NFC) devices are increasingly used in avariety of applications to communicate data. In NFC communication, afirst NFC device is positioned sufficiently close (e.g., a few inches orless) to another NFC device, such as an NFC reader, so that the devicesare inductively coupled. Load modulation is often used to communicatedata. In this regard, the reader may transmit a wireless carrier signal,and the NFC device may change the impedance of its antenna circuit inorder to modulate the carrier signal with data. The reader detects anddemodulates the modulated signal in order to recover the data.

NFC standards require the wireless carrier signal emitted from a readerto exhibit at least a certain threshold power at any point within aspecified three-dimensional (3D) test volume that extends a certaindistance (e.g., about 4 centimeters) from the reader. Ensuring that thereceive power of the carrier signal meets or exceeds the threshold atevery point in the test volume, particularly at the boundaries of thetest volume, can be problematic or result in inefficient powerconsumption. In this regard, one technique to ensure that the readermeets NFC specifications is to increase the reader's transmit power.However, such an increase undesirably increases the reader's powerrequirements, thereby reducing the useful life of its batteries.Further, reducing the reader's transmit power may affect the reader'sability to provide a suitable signal for satisfying NFC requirements atall points in the test volume. Improved techniques for enabling an NFCreader to comply with NFC standards while operating at reduced powerlevels are generally desired.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present disclosure, its nature andvarious advantages will be more apparent upon consideration of thefollowing detailed description, taken in conjunction with theaccompanying drawings in which:

FIG. 1 shows an illustrative block diagram of a payment system inaccordance with some embodiments of the present disclosure;

FIG. 2 depicts an illustrative block diagram of a payment device andpayment terminal in accordance with some embodiments of the presentdisclosure;

FIG. 3 depicts an illustrative payment reader and NFC device inaccordance with some embodiments of the present disclosure;

FIG. 4 depicts an illustrative block diagram of a payment reader inaccordance with some embodiments of the present disclosure;

FIG. 5 depicts an illustrative graph of impedance versus frequency foran antenna circuit of an NFC device in accordance with some embodimentsof the present disclosure;

FIG. 6 depicts an illustrative graph of voltage versus frequency forsignals received from an NFC device at multiple distances in accordancewith some embodiments of the present disclosure;

FIG. 7 depicts a top view of an illustrative payment reader inaccordance with some embodiments of the present disclosure;

FIG. 8 depicts a top view of an illustrative payment reader inaccordance with some embodiments of the present disclosure;

FIG. 9 depicts an illustrative antenna for a payment reader inaccordance with some embodiments of the present disclosure; and

FIG. 10 depicts a flow chart illustrating an exemplary process ofdetermining a location of an NFC in accordance with some embodiments ofthe present disclosure;

FIG. 11 depicts an illustrative block diagram of a payment reader inaccordance with some embodiments of the present disclosure;

FIG. 12 depicts an illustrative block diagram of a payment reader inaccordance with some embodiments of the present disclosure;

FIG. 13 depicts a top view of an illustrative payment reader inaccordance with some embodiments of the present disclosure; and

FIG. 14 depicts a side view of an illustrative payment reader inaccordance with some embodiments of the present disclosure.

DETAILED DESCRIPTION

The present disclosure generally pertains to systems and methods fordetermining a location of a near field communication (NFC) device. Insome embodiments of the present disclosure, an NFC reader communicateswith a remote NFC device using load modulation, as described above. Inthis regard, the NFC reader transmits a wireless carrier signal from anantenna, and the remote NFC device modulates such carrier signal bychanging its internal impedance in order to transmit data to the NFCreader. The NFC reader has at least one antenna for receiving the signalthat is load modulated by the remote NFC device. This antenna is coupledto circuitry that measures a spectrum of the received signal andidentifies a resonant frequency of the NFC device based on the measuredspectrum. The circuitry also determines the signal's amplitude at suchresonant frequency and precisely estimates the distance of the remoteNFC device from the antenna and, hence, reader based on such amplitude.By estimating the precise distance of the remote NFC device from thereader, the location of the remote NFC device relative to the reader canbe precisely determined, and this information may be used to operate theNFC reader more efficiently.

As an example, the precise location of the remote NFC device from thereader may be used to tune the communication characteristics of thereader such that the power of the carrier signal received by the remoteNFC device from the reader is higher. Thus, the NFC reader may operateat a lower transmit power relative to the transmit power that wouldotherwise be required in order to ensure compliance with applicable NFCstandards for certification.

In some embodiments, the NFC reader has multiple antennas that arepositioned at different locations on the reader. As described above,each antenna is coupled to circuitry that precisely measures arespective distance of the remote NFC device from the antenna based onthe resonant frequency identified within the spectrum of a signalreceived by the antenna. The distances from multiple antennas may beused to determine the location of the remote NFC device relative to thereader in three dimensional (3D) space. In other embodiments, thedistance measured by the circuitry for at least one of the antennas maybe combined with data from other sensors to determine the location ofthe remote NFC device in 3D space.

In some embodiments, one of a plurality of antennas is selected fortransmitting to the remote NFC device based on the determined locationof the remote NFC device relative to the reader. As an example, theantenna that is better aligned with (e.g., closest to) the remote NFCdevice may be selected for transmitting the reader's wireless carriersignal. Thus, the NFC reader may operate at a lower transmit powerrelative to the transmit power that would otherwise be required in orderto ensure compliance with applicable NFC standards for certification.

In some embodiments, the circuitry that is used to measure a spectrum ofthe signal received from the remote NFC device may also be used forother measurements with the reader, such as analyzing a signal from avirtual cage for sensing a tamper attempt. In addition, the spectrummeasured by the circuitry for at least one antenna may be used detect adevice type for the remote NFC device for use in processing informationfrom the remote NFC device. As an example, if the remote NFC device is apayment device, such as a credit card, the reader may detect a type ofpayment device being used for use in processing a payment transaction.To identify device type, the NFC reader may identify physicalcharacteristics of the remote NFC that are unique relative to otherdevice types. Such physical characteristics may include the resonantfrequency and amplitude of impedance loading from the device's antennacircuit. In some cases, based on the resonant frequency identified forthe remote NFC device, the reader may detect a problem with the remoteNFC device, such as damage to the antenna circuit of the remote NFCdevice. In yet other embodiments, the information about the receivedsignal may be used for other purposes.

For illustrative purposes, various embodiments of an NFC communicationsystem will be described in the context of payment systems that processpayment transactions. However, it should be emphasized that the conceptsdescribed herein may be applied to other types of NFC communicationsystems as may be desired.

FIG. 1 depicts an illustrative block diagram of a payment system 1 thatutilizes NFC communication in accordance with some embodiments of thepresent disclosure. In one embodiment, payment system 1 includes apayment device 10, payment terminal 20, network 30, and payment server40. In an exemplary embodiment, payment server 40 may include aplurality of servers operated by different entities, such as a paymentservice system 50 and a bank server 60. These components of paymentsystem 1 facilitate electronic payment transactions between a merchantand a customer.

The electronic interactions between the merchant and the customer takeplace between the customer's payment device 10 and the merchant'spayment terminal 20. The customer has a payment device 10, such as acredit card having a magnetic stripe, a credit card having anexternally-driven processing device such as an EMV chip, or anNFC-enabled electronic device such as a smart phone running a paymentapplication. The merchant has a payment terminal 20 such as a merchantdevice, payment reader, standalone terminal, combined customer/merchantterminals, electronic device (e.g., smart phone) running a point-of-saleapplication, or other electronic device that is capable of processingpayment information (e.g., encrypted payment card data and userauthentication data) and transaction information (e.g., purchase amountand point-of-purchase information).

In some embodiments (e.g., for low-value transactions or for paymenttransactions that are less than a payment limit indicated by an NFC orEMV payment device 10), the initial processing and approval of thepayment transaction may be processed at payment terminal 20. In otherembodiments, payment terminal 20 may communicate with payment server 40over network 30. Although payment server 40 may be operated by a singleentity, in one embodiment payment server 40 may include any suitablenumber of servers operated by any suitable entities, such as a paymentservice system 50 and one or more banks of the merchant and customer(e.g., a bank server 60). The payment terminal 20 and the payment server40 communicate payment and transaction information to determine whetherthe transaction is authorized. For example, payment terminal 20 mayprovide encrypted payment data, user authentication data, purchaseamount information, and point-of-purchase information to payment server40 over network 30. Payment server 40 may determine whether thetransaction is authorized based on this received information as well asinformation relating to customer or merchant accounts, and respond topayment terminal 20 over network 30 to indicate whether or not thepayment transaction is authorized. Payment server 40 may also transmitadditional information such as transaction identifiers to paymentterminal 20.

Based on the information that is received at payment terminal 20 frompayment server 40, the merchant may indicate to the customer whether thetransaction has been approved. In some embodiments such as a chip cardpayment device, approval may be indicated at the payment terminal, forexample, at a display device of a payment terminal. In other embodimentssuch as a smart phone or watch operating as an NFC payment device,information about the approved transaction and additional information(e.g., receipts, special offers, coupons, or loyalty programinformation) may be provided to the NFC payment device for display at ascreen of the smart phone or watch or storage in memory.

During transactions involving an EMV card, the EMV card may be insertedinto a card slot of the payment terminal. The terminal may make a numberof electrical connections with the EMV card including, inter alia, apower line, a ground line, a clock source line and a data line. The EMVcard may have at least one processor that is powered by the power andground lines, and that performs various functions in conjunction withthe payment terminal, such as encryption and communication of card andtransaction information, for example via an authorization requestcryptogram (ARQC) and other transaction information.

FIG. 2 depicts an illustrative block diagram of payment device 10 andpayment terminal 20 in accordance with some embodiments of the presentdisclosure. Although it will be understood that payment device 10 andpayment terminal 20 of payment system 1 may be implemented in anysuitable manner, in one embodiment the payment terminal 20 may comprisea payment reader 22 and a merchant device 29 (either or which may be anNFC device as will be described in more detail below). However, it willbe understood that as used herein, the term payment terminal may referto any suitable component of the payment terminal, such as paymentreader 22. In an embodiment, the payment reader 22 of payment terminal20 may be a device that facilitates transactions between the paymentdevice 10 and a merchant device 29 running a point-of-sale application.

In one embodiment, payment device 10 may be a device that is capable ofcommunicating with payment terminal 20 (e.g., via payment reader 22),such as an NFC device 12 or an EMV chip card 14 (which also may be anNFC device capable of communicating with the payment reader 22 via NFC).Chip card 14 may include a secure integrated circuit that is capable ofcommunicating with a payment terminal such as payment terminal 20,generating encrypted payment information, and providing the encryptedpayment information as well as other payment or transaction information(e.g., transaction limits for payments that are processed locally) inaccordance with one or more electronic payment standards such as thosepromulgated by EMVCo. In some embodiments, chip card 14 may include anEMV chip that is an externally-driven processing device that receivessignals necessary to operate the EMV chip (e.g., power, ground, andclock signals) from an external source. Chip card 14 may include contactpins for communicating with payment reader 22 (e.g., in accordance withISO 7816) and in some embodiments, may be inductively coupled to paymentreader 22 via a near field 15. A chip card 14 that is inductivelycoupled to payment reader 22 may communicate with payment reader 22using load modulation of a wireless carrier signal that is provided bypayment reader 22 in accordance with a wireless communication standardsuch as ISO 14443.

NFC device 12 may be an electronic device such as a smart phone, tablet,or smart watch that is capable of engaging in secure transactions withpayment terminal 20 (e.g., via communications with payment reader 22).NFC device 12 may have hardware (e.g., a secure element includinghardware and executable code) and/or software (e.g., executable codeoperating on at least one processor in accordance with a host cardemulation routine) for performing secure transaction functions. During apayment transaction, NFC device 12 may be inductively coupled to paymentreader 22 via near field 15 and may communicate with payment terminal 20by active or passive load modulation of a wireless carrier signalprovided by payment reader 22 in accordance with one or more wirelesscommunication standards such as ISO 14443 and ISO 18092.

Although payment terminal 20 may be implemented in any suitable manner,in one embodiment payment terminal 20 may include a payment reader 22and a merchant device 29. The merchant device 29 runs a point-of-saleapplication that provides a user interface for the merchant andfacilitates communication with the payment reader 22 and the paymentserver 40. Payment reader 22 may facilitate communications betweenpayment device 10 and merchant device 29. As described herein, a paymentdevice 10 such as NFC device 12 or chip card 14 may communicate withpayment reader 22 via inductive coupling. This is depicted in FIG. 2 asnear field 15, which comprises a wireless carrier signal having asuitable frequency (e.g., 13.56 MHz) emitted from payment reader 22.

In one embodiment, payment device 10 may be a contactless payment devicesuch as NFC device 12 or chip card 14, and payment reader 22 and thecontactless payment device 10 may communicate by modulating the wirelesscarrier signal within near field 15. In order to communicate informationto payment device 10, payment reader 22 changes the amplitude and/orphase of the wireless carrier signal based on data to be transmittedfrom payment reader 22, resulting in a wireless data signal that istransmitted to the payment device. This signal is transmitted by anantenna of payment reader 22 that is tuned to transmit at 13.56 MHz, andif the payment device 10 also has a suitably tuned antenna within therange of the near field 15 (e.g., 0 to 10 cm), the payment devicereceives the wireless carrier signal or wireless data signal that istransmitted by payment reader 22. In the case of a wireless data signal,processing circuitry of the payment device 10 is able to demodulate thereceived signal and process the data that is received from paymentreader 22.

When a contactless payment device such as payment device 10 is withinthe range of the near field 15, it is inductively coupled to the paymentreader 22. Thus, the payment device 10 is also capable of modulating thewireless carrier signal via active or passive load modulation. Bychanging the tuning characteristics of the antenna of payment device 10(e.g. by selectively switching a parallel load into the antenna circuitbased on modulated data to be transmitted) the wireless carrier signalis modified at both the payment device 10 and payment reader 22,resulting in a modulated wireless carrier signal. In this manner, thepayment device is capable of sending modulated data to payment reader22.

In some embodiments, payment reader 22 also includes an EMV slot 21 thatis capable of receiving chip card 14. Chip card 14 may have contactsthat engage with corresponding contacts of payment reader 22 when chipcard 14 is inserted into EMV slot 21. Payment reader 22 provides powerand a clock signal to an EMV chip of chip card 14 through these contactsand payment reader 22 and chip card 14 communicate through acommunication path established by the contacts.

Payment reader 22 may also include hardware for interfacing with amagnetic strip card (not depicted in FIG. 2 ). In some embodiments, thehardware may include a slot that guides a customer to swipe or dip themagnetized strip of the magnetic strip card such that a magnetic stripreader can receive payment information from the magnetic strip card. Thereceived payment information is then processed by the payment reader 22.

Merchant device 29 may be any suitable device such as tablet paymentdevice 24, mobile payment device 26, or payment terminal 28. In the caseof a computing device such as tablet payment device 24 or mobile paymentdevice 26, a point-of-sale application may provide for the entry ofpurchase and payment information, interaction with a customer, andcommunications with a payment server 40. For example, a paymentapplication may provide a menu of services that a merchant is able toselect and a series of menus or screens for automating a transaction. Apayment application may also facilitate the entry of customerauthentication information such as signatures, PIN numbers, or biometricinformation. Similar functionality may also be provided on a dedicatedpayment terminal 28.

Merchant device 29 may be in communication with payment reader 22 via acommunication path 23/25/27. Although communication path 23/25/27 may beimplemented via a wired (e.g., Ethernet, USB, FireWire, Lightning) orwireless (e.g., Wi-Fi, Bluetooth, NFC, or ZigBee) connection, in oneembodiment payment reader 22 may communicate with the merchant device 29via a Bluetooth low energy interface. In some embodiments, processing ofthe payment transaction may occur locally on payment reader 22 andmerchant device 29, for example, when a transaction amount is small orthere is no connectivity to the payment server 40. In other embodiments,merchant device 29 or payment reader 22 may communicate with paymentserver 40 via a public or dedicated communication network 30. Althoughcommunication network 30 may be any suitable communication network, inone embodiment communication network 30 may be the Internet and paymentand transaction information may be communicated between payment terminal20 and payment server 40 in an encrypted format such by a transportlayer security (TLS) or secure sockets layer (SSL) protocol.

FIG. 3 depicts an exemplary payment reader 22. The reader 22 may beconfigured to transmit wireless NFC signals to an NFC device 12 withinclose proximity to the reader 22. As an example, when the reader 22 issufficiently close to an NFC device 12 such that an antenna circuit 18of the reader 22 is inductively coupled to an antenna of the NFC device12, the reader 22 may transmit to the NFC device 12 a wireless carriersignal that is load modulated by the NFC device 12 in order to transmitpayment information for use in processing a payment transaction. The NFCdevice 12 may be referred to as “remote” from the reader in that it isnot physically connected to the reader and uses wireless signals tocommunicate.

Applicable NFC standards may require the wireless signal transmitted bythe reader 22 to exhibit an amplitude above a predefined threshold ateach point within a test volume 33. In some embodiments, the test volume33 may extend about 4 cm from the reader 22 and may be about 5 cm wide,but other dimensions of the test volume 33 are possible. By adhering tothe applicable NFC standards, the NFC device 12 should be able tocommunicate with the reader 22 with a certain minimum signal qualityregardless of its location within the test volume 33. In the context ofa payment system, the NFC device 12 may be a payment device, such as acredit card or a mobile telephone storing a payment application, butother types of NFC devices 12 are possible. In some embodiments, the NFCdevice 12 may be a test probe that is used to confirm whether the reader22 is in compliance with applicable NFC standards (e.g., to certify thereader 22).

FIG. 4 is a block diagram illustrating an exemplary embodiment of thereader 22. The exemplary embodiment shown by FIG. 4 has a transmitter 36that is coupled to an antenna 39, referred to hereafter for ease ofillustration as “transmit antenna 39.” The transmitter 36 is configuredto transmit a wireless carrier signal from the transmit antenna 39. Asdescribed above, an NFC device 12 (FIG. 3 ) within the test volume 33(FIG. 3 ) may be configured to receive and modulate the wireless carriersignal in order to communicate information to the reader 22. As shown byFIG. 4 , the reader 22 has at least one antenna, referred to hereafterfor ease of illustration as “receive antenna,” for receiving themodulated signal from the NFC device 12. In the exemplary embodimentshown by FIG. 4 , there are four receive antennas 41-44, but there maybe any number of receive antennas in other embodiments.

Each receive antenna 41-44 is coupled to a respective receiver 51-54, asshown by FIG. 4 , that receives and processes (e.g., filters andamplifies) the analog signal received from its corresponding antenna41-44. Each of the analog signals processed by the receivers 51-54 isreceived by an NFC decoder 56, which is configured to demodulate thesignal received by the antenna in order to recover and decode datatransmitted by the NFC device 12. That is, the NFC decoder 56 convertseach analog signal from the receivers 51-54 into a respective digitaldata stream defining information from the NFC device 12. A streamselector 57 may be configured to select one of the data streams forforwarding to other components of the reader 22 for further processing.As an example, the NFC device 12 may communicate payment information tobe used for completing a payment transaction. In such an embodiment, thestream selector 57 may select one of the streams from a respective oneof the receivers 51-54 for forwarding to payment processing circuitry58. Such data stream defines the payment processing information from theNFC device 12 and is used by the payment processing circuitry 58 inprocessing a payment transaction. In this regard, the payment processingcircuitry 58 may be coupled to a communication interface 61, such as acellular radio, that is configured to wirelessly transmit paymentinformation processed by the circuitry 58 to a payment server (not shownin FIG. 4 ) for approval of the payment transaction.

Each receiver 51-54 is also configured to provide the processed analogsignal to proximity detection circuitry 55 that then further processesthe signal in order to detect a proximity of the NFC device 12 relativeto the reader 22, as will be described in more detail below. Theproximity detection circuitry 55 may include one or more processors,field-programmable gate arrays (FPGAs), or other types of circuitry forperforming the functions ascribed to such circuitry 55 herein.

The proximity detection circuitry 55 is configured to transmit to tuningcircuitry 63 location data indicating the location of the payment device12 relative to the reader 22. The tuning circuitry 63 is configured totune communication characteristics of the transmitter 36 based on thelocation of the NFC device 12 relative to the reader 22. Specifically,the tuning circuitry 63 tunes the communication characteristics suchthat the received power of the wireless carrier signal at the locationof the NFC device 12 is higher, thereby helping to ensure thatapplicable NFC standards are satisfied. As an example, the transmitter36 may include variable capacitors and resistors that can be controlledby the tuning circuitry 63 in order to change the transmission profileof the wireless carrier signal, thereby changing the power of thecarrier signal at various points within the test volume 33. In addition,the tuning circuitry 63 may change the transmit power based on location,such as increasing transmit power when it is determined that the NFCdevice 12 is being moved to a dead zone or decreasing transmit powerwhen it is determined that the NFC device 12 is being moved away from adead zone. By optimizing the communication characteristics for thedetected location of the NFC device 12, it is possible for the reader 22to use a lower transmit power while still ensuring that the receivepower at the NFC device 12 is above a threshold specified by applicableNFC standards for the test volume 33. That is, the communicationcharacteristics may be tuned to ensure that the reader 22 remainscompliant with the applicable specifications pertaining to receive poweras the NFC device 12 is moved within the test volume 33.

Note that there are various techniques that may be used to detect thelocation of the NFC device 12 and, specifically for example, thedistance of the NFC device 12 from any of the receive antennas 41-44. Inone exemplary embodiment, the distance of the NFC device 12 from one ormore receive antennas 41-44 is precisely determined based on theresonant frequency of the antenna circuit 18 within the NFC device 12.

In this regard, the resonant frequency of the antenna circuit 18 of theNFC device 12 is the point where its impedance appears to be infinitelylarge or at open circuit. At other frequencies, the impedance of theantenna circuit 18 appears to be low. FIG. 5 depicts an exemplary graphof impedance versus frequency for an antenna circuit 18 where resonantfrequency is indicated by the peak of the curve. This high impedance atresonant frequency results in a substantial decrease in voltage for thesignals received by the receive antennas 41-44 of the reader 22 due tothe inductive coupling between the antennas of the reader 22 and the NFCdevice 12. Further, the amount of the decrease is a function ofdistance. Specifically, the magnitude of the voltage drop increases asthe NFC device 12 moves closer to the receive antennas 41-44 of thereader 22. To detect a distance of the NFC device 12 from a receiveantenna 41-44, the reader 22 is configured to identify the resonantfrequency of the antenna circuit 18 for the NFC device 12 and further todetect a change in voltage of the signal received by the receive antenna41-44 resulting from the high impedance at the resonant frequency.

In one exemplary embodiment, in order to detect a distance of the NFCdevice 12 from a receive antenna 41, the transmitter 36 is configured totransmit a continuous sine signal across a wide frequency band thatincludes the expected resonant frequency of the antenna circuit 18 forthe NFC device 12. The proximity detection circuitry 55 is configured tomeasure the voltage of the signal received by the antenna 41 from theNFC device 12 across the transmitted frequency band. As noted above,there will be a noticeable voltage drop at the resonant frequency of theantenna circuit 18 for the NFC device 12. FIG. 6 is a graph showingvoltage versus frequencies measured by the proximity detection circuitry55 when the NFC device is at different distances from the receiveantenna 41. Each curve of FIG. 6 indicates the spectrum of the signalreceived by the antenna 41 when the NFC device 12 is located at adifferent distance from the antenna 41.

Based on the measured spectrum of the signal received by the antenna 41,the proximity detection circuitry 55 identifies the NFC device'sresonant frequency within the spectrum, which is at the peak of thevoltage drop that results from the increased impedance of the antennacircuit 18 for the NFC device 12. The proximity detection circuitry 55determines the magnitude of the voltage drop at resonant frequency fromthe curve's normal profile for other frequencies and estimates the NFCdevice's distance from the antenna 41 based on the voltage drop. Suchestimation can be more precise relative to other techniques that may beused to estimate distance. However, in other embodiments, it is possibleto use other techniques to estimate distance.

In some embodiments, such as the embodiment shown by FIG. 4 , multiplereceive antennas 41-44 may be used, and information from each of themultiple antennas 41-44 may be processed by the proximity detectioncircuitry 55 to precisely determine the NFC device's location inthree-dimensional (3D) space. As an example, the proximity detectioncircuitry 55 may determine the x-coordinate, y-coordinate, andz-coordinate of the NFC device 12 in a coordinate system that isrelative to the reader 22.

In this regard, each receive antenna 41-44 may be at a differentlocation on the reader 22 in order to facilitate the process ofdetermining the location of the NFC device 12. FIG. 7 depicts anexemplary embodiment of the reader 22 for which the receive antennas41-44 are arranged to completely surround the transmit antenna 39 in thex-direction and the y-direction. In this regard, antennas 41 and 43 arelocated on opposite sides of the transmit antenna 39, and antennas 42and 44 are located on opposite sides of the transmit antenna 39. Asshown by FIG. 7 , it is possible for the receive antennas 41-44 tooverlap each other, as well as the transmit antenna 39. In someembodiments, the antennas may overlap in two dimensions (e.g., thex-direction and the y-direction, as shown by FIG. 7 ) with at least someof the antennas being in a different plane (e.g., the plane in thex-direction and y-direction). Indeed, as will be described in moredetail below, the transmit antenna 39 may be at a different z-coordinatethan any of the receive antennas 41-44. In other embodiments, otherpatterns and arrangements of the transmit antenna 39 and receiveantennas 41-44 are possible. Note that for simplicity of illustration,FIG. 7 shows antennas having a single turn, but each of the antennas maybe a conventional NFC antenna having many turns.

The proximity detection circuitry 55 may be configured to determine thedistance of the NFC device 12 from each receive antenna 41-44 using thedistance estimation techniques described above. After determining therespective distances of the NFC device 12 from the receive antennas41-44, the proximity detection circuitry 55 may use triangulation,trilateration, or other techniques for determining the coordinates ofthe NFC device 12 in 3D space relative to the reader 22. Suchcoordinates precisely indicate the location of the NFC device 12 withinthe test volume 33, and the tuning circuitry 63 may use such coordinatesto tune the communication characteristics of the transmitter 36, asdescribed above.

Note that the techniques for determining the location of the NFC device12 may be simplified by assuming that the NFC 12 is within or close tothe test volume 33. For example, using such assumption in combinationwith conventional triangulation or trilateration techniques, it may bepossible to determine the precise location of the NFC device 12 withinthe test volume 33 using just two receive antennas.

In some embodiments, the reader 22 may combine information from one ormore receive antennas 41-44 with information from other sources in orderto determine the location of the NFC device 12 in 3D space. As anexample, the reader 22 may include one or more sensors 75, as shown byFIG. 4 , that are configured to detect information that may be used todetermine one or more coordinates of the NFC device 12. In oneembodiment, the proximity detection circuitry 55 is configured to useinformation from the sensors 75 to determine the x-coordinate andy-coordinate of the NFC device 12 in a horizontal plane. In such anembodiment, the proximity detection circuitry 55 may use the distancedetermined from the signal received by one of the antennas 41-44 inorder to determine the z-coordinate or depth of the NFC device 12 in thez-direction, which is perpendicular to the horizontal plane. Thus, asingle receive antenna may be used in conjunction with the sensors 75 todetermine the precise location of the NFC device relative to the reader22 in 3D space.

Note that there are various types of sensors 75 that may be used todetermine one or more coordinates, such as the x-coordinate andy-coordinate, of the NFC device 12. As an example, it is possible forthe sensors 75 to include one or more proximity sensors that measuredistance or sense objects within a certain range. Such sensors maydetect objects by transmitting a signal and measuring an amount of thesignal that reflects from objects and returns to the sensor. As anexample, an optical sensor may be used to transmit an optical signal, ora sonar sensor may be used to transmit an acoustic signal. In otherembodiments, other types of sensors, such as capacitive sensors, may beused to sense a presence of the NFC device 12 or a distance of the NFCdevice from the respective sensor.

FIG. 8 shows an exemplary embodiment having a single receive antenna 41used in conjunction with a horizontal row 81 of proximity sensors 82 forsensing the location of the NFC device 12 in the x-direction and avertical row 83 of proximity sensors 82 for sensing the location of theNFC device 12 in the y-direction. In such an embodiment, each sensor 82may sense when the NFC device 12 is directly above the sensor 82. Thus,the proximity detection circuitry 55 may determine the x-coordinate ofthe NFC device 12 by determining which of the sensors 82 of row 81 aresensing a presence of the NFC device 12, and the proximity detectioncircuitry 55 may determine the y-coordinate of the NFC device 12 bydetermining which of the sensors 82 of row 83 are sensing a presence ofthe NFC device 12. In other embodiments, other types of sensors 75 andtechniques may be used to determine the coordinates of the NFC device12.

FIG. 9 depicts an exemplary looped antenna 90 having multiple pins 92that are electrically coupled to the proximity detection circuitry 55.In the exemplary embodiment shown by FIG. 9 , the proximity detectioncircuitry 55 is coupled to the pins 92 through a multiplexer (MUX) 94 sothat the proximity detection circuitry 55 receives signals fromdifferent pins serially rather than in parallel, but the use ofmultiplexer 94 is unnecessary in other embodiments.

For each pin 92, the proximity detection circuitry 55 is configured tomeasure the spectrum of the signal received from the pin 92 and to thenestimate the distance of the NFC device 12 from the pin 92 using thesame techniques described above for the receive antennas 41-44. Notethat the antenna 90 may have any number of pins 92 so that the proximitydetection circuitry 55 may have any number of data points fordetermining the location of the NFC device 12.

An exemplary operation and use of the system 1 will be described belowwith reference to FIG. 10 .

In this regard, assume that the reader 22 is currently communicatingwith an NFC 12 device that is within the test volume 33. In this regard,the communication characteristics of the transmitter 36 are such thatthe NFC device 12 receives a sufficient amount of power from thewireless carrier signal transmitted by the reader 22. That is, theamount of power received by the NFC device 12 exceeds a predefinedthreshold so that the reader 22 is in compliance with applicable NFCstandards. However, assume that the signal profile of the wirelesscarrier signal is such that there is a dead zone within the test volume33 at or near a boundary of the test volume 33. In this regard, if theNFC device 12 is moved to the dead zone without changing thecommunication characteristics of the transmitter 36, then the amount ofpower received by the NFC device 12 would fall below the predefinedthreshold so that the reader 22 is no longer compliant with NFCstandards. For illustrative purposes, assume that the NFC device 12 ismoved into this dead zone.

When the NFC 12 is moved into the dead zone, the reader 22 detects thechange in location of the NFC device 12 and then adjusts thecommunication characteristics of the transmitter 36 so that the NFCdevice 12 receives a suitable amount of power from the reader 22 inaccordance with applicable NFC standards. In this regard, for at leastone receive antenna 41-44, the proximity detection circuitry 55 of thereader 22 measures the spectrum of the signal received by such antenna41-44 across a range of frequencies, as shown by block 101 of FIG. 10 .Based on this measured spectrum, the proximity detection circuitry 55identifies the resonant frequency of the antenna circuit 18 for the NFCdevice 12, as shown by block 103. As described above, such resonantfrequency is at the peak of the voltage drop resulting from theincreased impedance of the NFC device's antenna circuit 18.

As shown by block 106 and 109, the proximity detection circuitry 55 ofthe reader 22 determines the amplitude of the received signal atresonant frequency and determines a distance of the NFC device 12 fromthe receive antenna based on this amplitude. As an example, theproximity detection circuitry 55 may determine a voltage drop of thesignal at the resonant frequency and convert this voltage drop into adistance estimate. Specifically, the reader 22 may include one or moretables that can be used by the proximity detection circuitry 55 to lookup or otherwise find the distance of the NFC device 12 from the readerusing amplitude or voltage drop at the resonant frequency as a lookupkey. In other embodiments, the proximity detection circuitry 55 maycalculate the distance using a predefined formula that is based on themeasured amplitude or voltage drop.

As shown by block 112, the proximity detection circuitry 55 determinesthe precise location of the NFC device 12 relative to the reader 22using at least the distance determined in block 109. As an example, theproximity detection circuitry 55 may perform blocks 101, 103, 106, and109 for multiple receive antennas and then use the estimated distancesto calculate the coordinates of the NFC device 12 in 3D space. Inanother example, the proximity detection circuitry 55 may use parameterssensed by sensors 75 to determine the x-coordinate and y-coordinate ofthe NFC device 12 and to use the distance estimated in block 109 todetermine the NFC device's z-coordinate. In other examples, othertechniques may be used to determine the location of the NFC device 12 in3D space based on the distance estimated in block 109.

Based on the location of the NFC device 12 determined in block 112, thereader 22 is configured to perform at least one operation for enhancingthe efficiency or operation of the reader 22, as shown by block 115 ofFIG. 10 . As an example, the tuning circuitry 63 may change thecommunication characteristics of the transmitter 36. In the instantexample where the NFC device 12 has been moved to a dead zone, thetuning circuitry 63 tunes the communication characteristics of thetransmitter 36 so that the NFC device 12 receives a greater amount ofpower from the reader 22. Specifically, the receive power is increasedby the tuning in the dead zone so that the NFC device 12 receives asufficient amount of power for the reader 22 to remain compliant withapplicable NFC standards. Thus, the reader 22 may operate at arelatively low power level that results in dead zones within the testvolume 33 but nevertheless remain compliant with applicable NFCstandards by adjusting the communication characteristics of thetransmitter 36 as the NFC device 12 is moved to different locations inthe test volume 33.

It should be emphasized that the above configurations and processes areexemplary, and various modifications may be made to the aforementionedembodiments. As an example, it is possible for components of theproximity detection circuitry 55 used to analyze the spectra of signalsreceived by the antennas 41-44 to also be used for measuring the spectraof other signals within the reader 22, as may be desired. In thisregard, as shown by FIG. 11 , the proximity detection circuitry 55 mayinclude a spectrum analyzer 133 for measuring the spectra of signals,such as the signals received by the antennas 41-44. Depending on itsdesign, the spectrum analyzer 133 has certain electrical components formeasuring spectra. As an example, the spectrum analyzer 133 may have anarrowband filter with an adjustable center frequency that can be sweptthrough a range of frequencies so that a voltage sensor can measure thevoltage of the received signal at multiple frequencies. In anotherembodiment, the spectrum analyzer 133 may have a Fourier transformdevice that transforms the received signal from the time domain to thefrequency domain to allow an analysis of the signal in the frequencydomain. The spectrum analyzer 133 may also have a signal generator thatvaries a frequency of its output so that it can sweep across a range offrequencies. These same components, such as filters, voltage sensors,Fourier transform devices, signal generators, and other devices that maybe used to measure a spectrum of a signal from at least one of thereceive antennas 41-44 may also be used to measure the spectrum of atleast one other signal in the reader 22.

As an example, the payment processing circuitry 58 may define a securearea for processing sensitive information such as personalidentification numbers (PINs) used in payment transactions. As shown byFIG. 11 , one or more components, such as a secure processor 138 forprocessing sensitive information of a payment transaction, may belocated in the secure area, which is protected from tampering attemptsby a virtual cage 141. As known in the art, the virtual cage 141 maycomprise a plurality of conductive traces that pass over the componentswithin the virtual cage 141 such that a hacker would need to touch ormodify (e.g., cut) at least one of the conductive traces in order tophysically access the components in the secure area.

The spectrum analyzer 133 of the proximity detection circuitry 55 may beelectrically coupled to the traces of the virtual cage 141 and transmita probe signal through the traces of the virtual cage 141. The spectrumanalyzer 133 may also analyze the response (i.e., the probe signal afterpassing through the virtual cage) to determine the spectrum of thereceived signal. In particular, the same components of the spectrumanalyzer 133 used to measure the spectrum of a signal from at least onereceive antenna 41-44, such as the filter, voltage sensor, or Fouriertransform device described above, may also be used to measure thespectrum of the signal received from the virtual cage 141. If themeasured spectrum from the virtual cage 141 materially changes (e.g.,the voltage at one or more frequencies changes by at least a thresholdamount), the proximity detection circuitry 133 may be configured todetect a tamper attempt. In response to such detection of a tamperevent, the proximity circuitry 133 may take one or more actions, such astransmitting a warning message or disabling one or more components orfunctions of the reader 22. Moreover, using the same components of thespectrum analyzer 133 to measure spectra of different signals within thereader 22 helps to reduce the circuitry within and the overall cost ofthe reader 22.

In some embodiments, the proximity detection circuitry 55 may beconfigured to detect a problem with the NFC device 12 based on thespectrum of the signal received from it. In this regard, certain typesof NFC devices 12 are expected to have resonant frequencies within acertain frequency range. As an example, a design of an NFC device 12from a first issuing bank may be expected to have a resonant frequencyin one range, and an NFC device 12 from another issuing bank may beexpected to have a resonant frequency in another range. In the contextof test probes, there may be multiple types of test probes that could beused to certify the reader 22. The proximity detection circuitry 55 mayinclude memory for storing predefined data indicating the expectedresonant frequency range for the NFC device 12. If there are multipletypes of NFC devices 12 with different frequency ranges, the proximitydetection circuitry 55 may store the expected resonant frequency rangefor each device type.

When the proximity detection circuitry 55 identifies the resonantfrequency for the antenna circuit 18 of the NFC device 12, it isconfigured to compare the measured resonant frequency to the expectedresonant frequency for the NFC device 12 stored in memory. If themeasured resonant frequency is outside of this range, the proximitydetection circuitry 55 may be configured to detect a problem with theNFC device and report the problem to a user. As an example, the resonantfrequency of the NFC device 12 may be outside of the expected range whenthe antenna circuit 18 has been damaged, which may impair the device'sability to reliably communicate with the reader 22. In such case, theproximity detection circuitry 55 may be configured to transmit a warningmessage from the reader 22 using the communication interface 61 orotherwise to a server or other location so that corrective action may betaken. As an example, the reader 22 may transmit the warning message tothe payment server to be used for approving the payment transaction sothat the issuing bank may take corrective action, such as issuing a newNFC device 12 to the consumer making the purchase. In other embodiments,other types of corrective actions may be taken.

The reader 22 may also be configured to tailor its communicationcharacteristics based on the determined device type for the NFC device12. In this regard, the tuning circuitry 63 may adjust the communicationcharacteristics of the transmitter 36 based on the device typedetermined by the proximity detection circuitry 55. In some cases, thetuning circuitry 63 may tune the communication characteristics based onboth device type and the location of the NFC device 12. In someembodiments, device type may be determined based on data communicatedfrom the NFC device 12, such as an account number or other paymentinformation, to be used in a payment transaction. In other embodiments,device type may be determined based on the characteristics of a signalreceived from the NFC device 12. As an example, the proximity detectioncircuitry 55 may identify device type based on the device's resonantfrequency, as determined by the circuitry 55 according to the techniquesdescribed above. Other physical characteristics indicated by thespectrum of the received signal, such as the amplitude of impedanceloading may also be used to identify device type. In other embodiments,other techniques for determining device type are possible.

In some embodiments, the location of the NFC device 12 may be used toperform other functions in the reader 22 in addition to or in lieu oftuning the transmitter 36. As an example, the location of the NFC device12 may be used to select one or more transmit antennas for communicatingwith the NFC device 12. FIG. 12 depicts an exemplary embodiment of areader 22 having a plurality of transmit antennas 161-164. In theembodiment shown by FIG. 12 , each transmit antenna 161-164 is coupledto the transmitter 36 through a multiplexer 172. However, otherconfigurations are possible in other embodiments. As an example, it ispossible for each transmit antenna 161-164 to be coupled to a respectivetransmitter without the use of a multiplexer.

Each transmit antenna 161-164 is preferably positioned at a differentlocation on the reader 22. As an example, FIG. 13 shows an exemplaryembodiment for which the transmit antennas 161-164 are positioned atdifferent locations and are overlapping. Other patterns and locations ofthe antennas 161-164 are possible in other embodiments.

Once the proximity detection circuitry 55 has determined the location ofthe NFC device 12, as described above, the circuitry 55 may beconfigured to selectively enable the transmit antennas 161-164 based onthe determined location of the NFC device 12. As an example, theproximity detection circuitry 55 may enable the transmit antenna that isbetter aligned with (e.g., closest to) the NFC device 12 and to disablethe other transmit antennas. Thus, the signal strength of the wirelesscarrier signal received from the enabled transmit antenna should bestronger relative the signal strength of a wireless carrier that wouldbe transmitted from one of the other transmit antennas. If the NFCdevice 12 is moved to a different location so that it is better alignedwith another transmit antenna, then this other transmit antenna may beselected for communication with the NFC device. Thus, as the NFC device12 moves within the test volume 33, the antenna that is likely toprovide the strongest wireless carrier signal to the NFC device 12 isselected for communication and enabled while the other transmit antennasare disabled. Selective use of multiple transmit antennas 161-164 inthis way may help to eliminate dead zones within the test volume 33 andensure that the NFC device 12 receives a strong signal. That is,selection of the transmit antenna 161-164 to communicate with the NFCdevice 12 is optimized based on the NFC device's current location inorder to ensure that the NFC device 12 receives a strong signal from thereader 22 regardless of its location within the test volume 33.

Note that there are various techniques that can be used to enable anddisable the transmit antennas 161-164. In the embodiment depicted byFIG. 12 , the proximity detection circuitry 55 controls the multiplexer172 in order to control selection of the transmit antenna 161-164 to beused for communication. In this regard, the proximity detectioncircuitry 55 controls the multiplexer 172 such that the transmit antenna161-164 selected for communication receives the carrier signal from thetransmitter 36 while the remaining transmit antennas do not. In otherembodiments, other techniques for enabling and disabling the transmitantennas 161-164 are possible. As an example, if multiple transmitters36 are used, the proximity detection circuitry 55 may control thetransmitters such that only the one that is coupled to the transmitantenna 161-164 to be enabled actually transmits the carrier signal.

In other embodiments, it is possible for multiple transmit antennas161-164 to be enabled for communicating with the NFC device 12. However,enabling more than one transmit antenna 161-164 for communication hasvarious disadvantages that can be avoided by enabling only one transmitantenna 161-164 at a time. For example, enabling multiple transmitantennas 161-164 increases power requirements and can also createinterference between the multiple carrier signals that are beingtransmitted. Further, when multiple transmit antennas 161-164 are turnedon, it is possible for the antennas 161-164 to detune one another.Selecting only one transmit antenna 161-164 for communication helps toprovide a more efficient solution and, in particular, helps to reducepower and increase reliability of the data communications.

As described above, it is possible to use one or more receive antennas41-44 to receive signals that are used for both data communication andproximity detection of the NFC device 12. In addition, the streamselector 57 may be configured to select a data stream from one of thereceive antennas 41-44 for processing a payment transaction or othertype of transaction by the circuitry 58. As an example, cyclicredundancy check (CRC) data or other types of data used for detectingerrors may be included in the information transmitted by the NFC device12, and the stream selector 57 may be configured to use such informationto detect errors in the received data streams. The stream selector 57may be further configured to count the errors from each receive antenna41-44 over a given time window, and select the data stream from thereceive antenna 41-44 associated with the lowest error count. The streamselector 57 may then send the information from the selected data streamto the payment processing circuitry 58 for use in processing the paymenttransaction. In other embodiments, other techniques for selecting thedata stream to be used for the payment transaction are possible.

As an example, it is possible for the proximity detection circuitry 55to inform the stream selector 57 of the location of the NFC device 12and for the stream selector 57 to then select the data stream from thereceive antenna 41-44 that is better aligned with (e.g., closest to) theNFC device 12. In yet other embodiments, other techniques for selectingthe desired data stream to use for further processing are possible. Inaddition, in other embodiments, the information from the stream selector57 may be used for other purposes or types of transactions. That is, theuse of the reader 22 in performing payment transactions is unnecessary,and the reader 22 may be used in the same way as described above inorder to process other types of transactions.

Note that simultaneous use of multiple receive antennas 41-44, asdescribed above, does not have the same disadvantages that areassociated with simultaneous use of multiple transmit antennas 161-164.In this regard, the receive antennas 41-44 can be passive such that theydo not consume any power from the battery or other power resources ofthe reader 22. That is, the receive antennas 41-44 do not increase thepower requirements of the reader 22. Further, since the receive antennas41-44 are passive, they do not have a tuning circuit, and theirimpedance does not load the tuning circuitry 63.

In addition, there is not a stringent impedance requirement for passivereceive antennas 41-44. In some embodiments, transparent materials, suchas Indium Thin Oxide (ITO), may be used for the receive antennas 41-44instead of opaque materials having a higher conductance, such as copper.By using transparent materials, the receive antennas 41-44 can be placedon a surface of the reader 22 without adversely affecting the aestheticappearance of the reader to users. As an example, if the reader 22 has adisplay device, such as a liquid crystal display (LCD), the receiveantennas 41-44 could be placed on or near the surface of the displaydevice in view of the user without being significantly noticeable. Suchplacement of the receive antennas 41-44 may provide a larger receivearea, thereby helping to improve receive sensitivity. Further, placementof the antennas 41-44 on or near the surface of the display device orother surface of the reader 22 may prevent the display device or othercomponents of the reader 22 from significantly attenuating the signalreceived by the antennas 41-44. That is, such signal does not need topass through the display device or other components before beingreceived by the antennas 41-44.

FIG. 14 depicts an exemplary reader 22 having a display device 205, suchas an LCD, embedded in or otherwise coupled to the reader 22. As shownby FIG. 14 , the receive antennas 41-44 may be composed of a transparentmaterial and positioned on or near a surface of the display device 205.The transmit antennas 161-164, which may be composed of an opaquematerial, such as copper, may positioned on an opposite side of thedisplay device 205 such that the wireless carrier signal transmitted byone of the transmit antennas 161-164 passes through the display device205 before reaching the NFC device 12. Such placement of the transmitantennas 161-164 undesirably increases signal attenuation since thewireless carrier signal passes through the display device 205, but thetransmit antennas 161-164 are hidden by the display device 205 so thatthey do not adversely affect the aesthetic appearance of the reader 22.In other embodiments, other configurations and placement of the antennas41-44 and 164-164 are possible.

Note that, in several embodiments described above, the circuitry of thereader 22 is shown as disparate blocks for illustrative purposes. It isunnecessary for the circuitry to be separated or segmented in anymanner, and it is possible for the same set of circuitry to be used formultiple blocks. As an example, the term “circuitry” may be used torefer to any block of circuitry shown by the figures or to refercollectively to multiple blocks. As an example, circuitry may include aprocessor that is programmed with instructions for performing functionsof the tuning circuitry 63, functions of the proximity detectioncircuitry 55, and/or functions of the payment processing circuitry 58.Moreover, the same hardware resources, such as one or more processors orother types of circuitry, may be used to implement the functionality ofmultiple blocks.

The foregoing is merely illustrative of the principles of thisdisclosure and various modifications may be made by those skilled in theart without departing from the scope of this disclosure. The abovedescribed embodiments are presented for purposes of illustration and notof limitation. The present disclosure also can take many forms otherthan those explicitly described herein. Accordingly, it is emphasizedthat this disclosure is not limited to the explicitly disclosed methods,systems, and apparatuses, but is intended to include variations to andmodifications thereof, which are within the spirit of the followingclaims.

As a further example, variations of apparatus or process parameters(e.g., dimensions, configurations, components, process step order, etc.)may be made to further optimize the provided structures, devices andmethods, as shown and described herein. In any event, the structures anddevices, as well as the associated methods, described herein have manyapplications. Therefore, the disclosed subject matter should not belimited to any single embodiment described herein, but rather should beconstrued in breadth and scope in accordance with the appended claims.

What is claimed is:
 1. A near field communication (NFC) system,comprising: an NFC device configured to receive a wireless carriersignal and modulate the wireless carrier signal with data; and an NFCreader having a transmit antenna and a plurality of passive receiveantennas, the NFC reader configured to wirelessly transmit the wirelesscarrier signal via the transmit antenna and receive the modulatedwireless carrier signal with the plurality of passive receive antennas,the NFC reader having circuitry configured to provide a plurality ofdata streams based on the modulated wireless carrier signal, each of theplurality of data streams defining data recovered from the modulatedwireless carrier signal received from a respective one of the pluralityof receivers, the circuitry further configured to select, based on alocation of the NFC device relative to the NFC reader, one of theplurality of data streams for use in processing a transaction.
 2. TheNFC reader of claim 1, wherein at least one of the plurality of passivereceive antennas is positioned on a surface of the NFC reader.
 3. TheNFC reader of claim 2, wherein the at least one of the plurality ofpassive receive antennas is composed of a transparent material.
 4. TheNFC reader of claim 3, wherein the transparent material is Indium ThinOxide (ITO).
 5. The NFC system of claim 1, wherein the circuitrycomprises a stream selector and payment processing circuitry, the streamselector configured to select one of the plurality of data streams forforwarding to the payment processing circuitry, wherein the paymentprocessing circuitry is configured to receive the selected one of theplurality of data streams and to process a payment transaction based onthe selected one of the plurality of digital data streams.
 6. The NFCreader of claim 5, wherein the stream selector is configured to compareerrors associated with each of the plurality of digital data streams andto select the one of the plurality of digital data streams based oncomparisons of the errors.
 7. The NFC reader of claim 5, wherein thecircuitry is configured to detect a location of the NFC device, andwherein the stream selector is configured to select the one of theplurality of digital data streams based on the detected location of theNFC device.
 8. A near field communication (NFC) reader, comprising: atransmit antenna; a transmitter coupled to the transmit antenna andconfigured to transmit a wireless carrier signal from the transmitantenna; a plurality of passive receive antennas; a plurality ofreceivers coupled to the plurality of passive receive antennas forreceiving from the plurality of passive receive antennas the wirelesscarrier signal modulated with data from an NFC device; and circuitryconfigured to provide a plurality of data streams, each of the pluralityof data streams defining data recovered from the wireless carrier signalreceived by a respective one of the plurality of receivers, thecircuitry further configured to select, based on a location of the NFCdevice relative to the NFC reader, one of the plurality of data streamsfor use in processing a transaction.
 9. The NFC reader of claim 8,wherein at least one of the plurality of passive receive antennas ispositioned on a surface of the NFC reader.
 10. The NFC reader of claim9, wherein the at least one of the plurality of passive receive antennasis composed of a transparent material.
 11. The NFC reader of claim 10,wherein the transparent material is Indium Thin Oxide (ITO).
 12. The NFCreader of claim 8, wherein the circuitry is configured to compare errorsassociated with each of the plurality of data streams and to select theone of the plurality of data streams based on comparisons of the errors.13. The NFC reader of claim 8, wherein the circuitry is configured todetect the location of the NFC device and to select the one of theplurality of data streams based on the detected location of the NFCdevice.
 14. The NFC reader of claim 8, wherein the transaction is apayment transaction.
 15. A method for use with a near fieldcommunication (NFC) reader, comprising: transmitting a wireless carriersignal from a transmit antenna of the NFC reader; receiving, with aplurality of receivers from passive receive antennas of the NFC reader,the wireless carrier signal modulated with data from an NFC device;providing a plurality of data streams, each of the plurality of datastreams defining data recovered from the wireless carrier signalreceived by a respective one of the plurality of receivers; selecting,with circuitry of the NFC reader based on a location of the NFC devicerelative to the NFC reader, one of the plurality of data streams for usein processing a transaction; and processing, with the NFC reader, thetransaction using the selected data stream.
 16. The method of claim 15,wherein at least one of the plurality of passive receive antennas ispositioned on a surface of the NFC reader.
 17. The method of claim 16,wherein the at least one of the plurality of passive receive antennas iscomposed of a transparent material.
 18. The method of claim 17, whereinthe transparent material is Indium Thin Oxide (ITO).
 19. The method ofclaim 15, further comprising comparing, with the circuitry, errorsassociated with each of the plurality of data streams, wherein theselecting is based on the comparing.
 20. The method of claim 15, furthercomprising detecting the location of the NFC device with the circuitry,wherein the selecting is based on the detected location of the NFCdevice.